• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7438-7442
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• 2014

An assessment of flocculation was performed by measuring the distribution of the floc size during sedimentation in water works. The size and number of flocs have a greater effect on an evaluation of the efficiency of flocculation rather than the turbidity. The data was collected in situ using particle image velocimetry and image analysis. The measurements were carried out at a water depth of 1m. The removal efficiency of the total organic compounds, UV absorbance and turbidity depended on the size and floc size distribution in flocculation as the G value. The G value of 50 sec-1, 30 sec-1 and 10 sec-1 showed the highest degree of efficiency in the case of an inlet water turbidity of 5 NTU, and the highest degree of efficiency was observed at a G value of 65 sec-1, 40 sec-1 and 10 sec-1 when the inlet water turbidity was 263 NTU. The number of flocs with a distribution of above $1,200{\mu}m$ was 14. The dynamics between two important growth mechanisms were investigated as the energy input changed. This is a certain method that makes use of the size and number of flocs as an efficiency assessment.

• Journal of the Korean earth science society
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• v.32 no.4
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• pp.402-410
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• 2011

We present results of CO observations toward an infrared (IR) source, IRAS 07280-1829, and its possibly related molecular clouds. The physical parameters of this IR source such as its infrared slope (${\alpha}$=16) of the Spectral Energy Distribution and bolometric temperature (145 K) indicate that it is an embedded protostar. Its luminosity is ${\sim}2.9{\times}10^4L_{\odot}$, typical of a massive star. The CO profile toward IRAS 07280-1829 has broad wing components, implying a possible existence of CO outflow. The excitation temperature and mass of a molecular cloud (Cloud A) which is thought to harbor the IR source are estimated to be 9~22 K and ~180 $M_{\odot}$, respectively, indicating the Cloud A is a typical infrared-dark cloud. Its LTE mass is found to be much smaller than its virial mass by more than a factor of 10 which is inconsistent with the fact that a protostar recently formed exists in the Cloud A. This may suggest that the environment of the cloud where the IR source is forming is dominant of turbulence and/or magnetic filed, making its virial mass estimated unusually high.

• Journal of The Korean Association For Science Education
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• v.35 no.3
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• pp.509-521
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• 2015

Argumentation is a social and collaborative dialogic process. A large number of researchers have focused on analyzing the structure of students' argumentation occurring in the scientific inquiry context, using the Toulmin's model of argument. Since SSI dialogic argumentation often presents distinctive features (e.g. interdisciplinary, controversial, value-laden, etc.), Toulmin's model would not fit into the context. Therefore, we attempted to develop an analytical framework for SSI dialogic argumentation by addressing the concepts of 'discourse clusters' and 'discourse schemes.' Discourse clusters indicated a series of utterances created for a similar dialogical purpose in the SSI contexts. Discourse schemes denoted meaningful discourse units that well represented the features of SSI reasoning. In this study, we presented six types of discourse clusters and 19 discourse schemes. We applied the framework to the data of students' group discourse on SSIs (e.g. euthanasia, nuclear energy, etc.) in order to verify its validity and applicability. The results indicate that the framework well explained the overall flow, dynamics, and features of students' discourse on SSI.

• Economic and Environmental Geology
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• v.47 no.2
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• pp.193-204
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• 2014

Shale gas has caused a change in the dynamics of gas market since development of horizontal drilling technic and hydraulic fracturing technic caused its commercial production. The commercial amount of shale gas is 187.5 trillions $m^3$ so human can use it for 59 years and the amount will increase in the future. Several nations such as USA, Canada, China and Russia have more and more interested in shale gas as a futuristic major energy source. In accordance with this trend in the world, the amount of studying theses for development of shale gas have increased so their theses became important increasingly. The number of searched theses (1986 ~ The first half of 2013) is 3,468 and has increased recently. Among 89 nations studying shale gas, USA has 637 theses as No.1 in the world. 1,813 global studying institutes have studied shale gas; in the analysis result of several studying institutes, US geological survey institute was ranked as No.1 for the quality level of shale gas study and intensity of global cooperation.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.417-423
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• 2007

Oxy-gasification or oxygen-blown gasification, enables a clean and efficient use of coal and opens a promising way to CO2 capture. The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. The purposes of this study are to develop an evaluation technique for design and performance optimization of coal gasifiers using a numerical simulation technique, and to confirm the validity of the model. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization, mixture fraction model and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The influence of turbulence on the gas properties was taken into account by the PDF (Probability Density Function) model. A numerical simulation with the coal gasification model is performed on the Conoco-Philips type gasifier for IGCC plant. Gas temperature distribution and product gas composition are also presented. Numerical computations were performed to assess the effect of variation in oxygen to coal ratio and steam to coal ratio on reactive flow field. The concentration of major products, CO and H2 were calculated with varying oxygen to coal ratio (0.2-1.5) and steam to coal ratio(0.3-0.7). To verify the validity of predictions, predicted values of CO and H2 concentrations at the exit of the gasifier were compared with previous work of the same geometry and operating points. Predictions showed that the CO and H2 concentration increased gradually to its maximum value with increasing oxygen-coal and hydrogen-coal ratio and decreased. When the oxygen-coal ratio was between 0.8 and 1.2, and the steam-coal ratio was between 0.4 and 0.5, high values of CO and H2 were obtained. This study also deals with the comparison of CFD (Computational Flow Dynamics) and STATNJAN results which consider the objective gasifier as chemical equilibrium to know the effect of flow on objective gasifier compared to equilibrium. This study makes objective gasifier divided into a few ranges to study the evolution of the gasification locally. By this method, we can find that there are characteristics in the each scope divided.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.6
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• pp.807-817
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• 2008

Steers with ad libitum access to rice straw were assigned to four diets to evaluate the effects of maize or soybean hull supplementation on intake, in vivo digestibility, ruminal pH, VFA, ammonia-nitrogen ($NH_3-N$) and in situ ruminal disappearance of feed nutrients by cattle consuming rice straw. Supplement treatments were: no supplement (RS); soybean meal at 0.127% BW (SBM); cracked maize at 0.415% BW plus 0.044% BW soybean meal (MAIZE); or soybean hulls at 0.415% BW plus 0.044% BW soybean meal (HULLS). The MAIZE and HULLS diets were formulated to provide approximately 4 MJ of $NE_m$ per kg of diet. Rice straw DMI was not affected (p = 0.34) by supplement. Apparent dry matter (DM) digestibility was greater (p<0.001) for MAIZE and HULLS (56.6 and 60.0%, respectively) than for steers consuming SBM or RS (51.8 and 44.4%, respectively). Apparent NDF digestibility was greater (p<0.0004) for HULLS than MAIZE (61.7 vs. 58.0%, respectively) and apparent ADF digestibility was greater (p<0.0008) for HULLS than MAIZE (61.1 vs. 49.2%, respectively). There was no difference in apparent hemicellulose digestibility (p = 0.43). Analysis of ruminal fluid collected 0, 2, 4, 6, and 8 h post-feeding revealed ammonia-nitrogen was greatest (p<0.05) for steers on SBM and HULLS diets at 2 h (24.08 and 22.57 mg/dl, respectively) and total volatile fatty acids was greatest (p<0.05) for HULLS at 4 h (230 mM/L). In situ disappearance, measured at 0, 2, 4, 6, 8, 16 and 24 h, indicated that SBM, MAIZE and HULLS tended to enhance the digestibility of DM and fiber components of rice straw. In situ disappearance of rice straw DM was greatest for SBM and/or HULLS from 4 to 24 h (p = 0.03). Rice straw NDF and ADF disappearance was enhanced by supplementation from 16 to 24 h (p<0.02). Rice straw DM, NDF and ADF disappearances at 24 h were similar for MAIZE and HULLS treatments. When feeding cattle rice straw diets, energy and protein-based supplements are essential. This study showed that fiber-based supplements are just as, if not more, effective as starch-based supplements in rice straw utilization. This study shows that soybean hulls, in spite of their high fiber content, are as efficient as maize for supplementing rice straw primarily because fiber in soybean hulls is highly digestible as shown by in vivo digestibility and in situ disappearance.

• Applied Microscopy
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• v.41 no.4
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• pp.249-255
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• 2011

Neurons utilize a large quantity of energy for their survival and function, and thereby require active mitochondrial function. Mitochondrial morphology shows dynamic changes, depending on the cellular condition, and mitochondrial dynamics are required for neuronal development and function. In this study, we found that the length of mitochondria in the distal axon is significantly shorter than that of mitochondria in dendrites or proximal axons of cerebral cortical neurons, and the reason for this difference is the local fission within the axon. We also found that suppression of Drp1, a key regulator of mitochondrial fission, resulted in significant elongation of mitochondria in axons. Collectively, these results suggest that local mitochondrial fission within the axon contributes to region-dependent mitochondrial length differences in the axons of cortical neurons.

• Journal of Bio-Environment Control
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• v.29 no.3
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• pp.285-292
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• 2020

Because the inner environment of greenhouse has a direct impact on crop production, many studies have been performed to develop technologies for controlling the environment in the greenhouse. However, it is difficult to apply the technology developed to all greenhouses because those studies were conducted through empirical experiments in specific greenhouses. It takes a lot of time and cost to develop the models that can be applicable to all greenhouse in real situation. Therefore studies are underway to solve this problem using computer-based simulation techniques. In this study, a model was developed to predict the inner environment of glass greenhouse using CFD simulation method. The developed model was validated using primary and secondary heating experiment and daytime greenhouse inner temperature data. As a result of comparing the measured and predicted value, the mean temperature and uniformity were 2.62℃ and 2.92%p higher in the predicted value, respectively. R² was 0.9628, confirming that the measured and the predicted values showed similar tendency. In the future, the model needs to improve by applying the shape of the greenhouse and the position of the inner heat exchanger for efficient thermal energy management of the greenhouse.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.12
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• pp.706-713
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• 2017

This study compared and analyzed the water treatment efficiency and the applicability of water treatment plant using the existing Mechanical Rapid-Mixer by introducing the Non-powered Vortex Mixer to the domestic water treatment plant. For this study, fluid flow characteristics and head loss of a Non-powered Vortex Mixer are calculated by Computational Fluid Dynamics (CFD)respectively. The head loss rate inside the mixer was 11.30% when the inflow velocity was 0.5 m/sec, 16.27% at 0.6 m/sec and 21.44% at 0.7 m/sec, the head loss rapidly increased at the optimal velocity of 0.5 m/sec. For the inflow velocity of 0.5 m/sec, the turbulent intensity at the inlet was 2.37% and at the outlet was 7.83%, so there was sufficient mixing strength for the particulate matter and the coagulant. The result of the water quality of the treatment plants with the inflow velocity of 0.38 m/sec that was operated in three years after replacing all 12 units of the existing Rapid-Mixer with the Non-powered Mixer met the standards. Hence, it is possible to reduce the energy consumption of 64,143 ~ 65,306 kWh/year since the Rapid-Mixer is replaced by the Non-powered Vortex Mixer.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.443-448
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• 2015

A swirl type mixer was developed to improve the flow mixing performance of a marine selective catalytic reduction system. In this study, the swirl type mixer and a multi-staged swirl type mixer, in which the angle of the vanes at each stage is controllable were considered to provide the optimal region of angles for the mixers. The effects of the vane angles in both mixers on the uniformity index and pressure drop were investigated using a computational fluid dynamics simulation. In the swirl type mixer, the optimal conditions for the flow mixing performance were observed at vane angles from 30 to 60 degrees when vane angles could be adjusted between 10 to 80 degrees, however, the pressure drop increased continually with increasing vane angle of the mixer. On the other hand, control of the individual staged angles of the multi-staged mixer showed that it is possible to keep enhancing flow mixing performance while reducing the pressure drop.